Toner adder brush roller and method for controlled installation of brush filament population

ABSTRACT

A method for controlled installation of a brush filament population on a shaft for making a toner adder brush roller includes applying a layer of adhesive over a surface of a roller shaft, applying a template over at least a portion of the shaft surface, and flocking a multiplicity of filaments on the shaft surface to provide a brush on the roller shaft having a filament population controlled by the application of the template. The method also includes removing the template from the shaft surface after flocking the multiplicity of filaments such that a set of filaments less than the multiplicity of filaments is removed with the template. The method further includes flocking additional filaments on the portion of the shaft surface after removing the template from the portion of the shaft surface, the additional filaments differs from said previously flocked filaments in one of material, length, denier, or combinations of the foregoing.

BACKGROUND

1. Field of the Invention

The present invention relates generally to toner cartridge systems, suchas used in laser printers and the like, and, more particularly, to atoner adder brush roller and method for controlled installation of abrush filament population on a shaft of a toner adder brush roller.

2. Description of the Related Art

A toner adder roller, also know as a toner supply roller, is the firstitem of hardware that toner encounters in a conventional laser printertoner cartridge. The toner adder roller is made from a conductive foamwhich is compressed against a harder developer roller. The developerroller and toner adder roller rotate and form a nip between one another.The role of the toner adder roller in the cartridge is two-fold: as afirst mechanism, applying fresh toner onto the developer roller; and, asa second mechanism, removing old toner from the developer rollersurface. Both mechanisms have electrostatic charge and mechanicalattributes.

The toner adder roller has been identified as one factor contributing totoner starvation in toner cartridges which ultimately leads to failureof a laser printer toner cartridge system. One theory is that starvationoccurs when the toner adder roller cannot sufficiently supply thedeveloper roller with fresh toner.

The toner starvation issue continues to pose a substantial problem andis only likely to become more pressing in view of the future need in themarket for higher print speeds and for cartridges that have longer printlife. The increased torque generated at higher speeds in combinationwith a longer cartridge life will only increase the toner starvationissue. In addition, the faster print speeds will require more strain onthe power train and will also generate more heat in the cartridge. Allthese effects mentioned above are expected to have negative impact onthe print quality and to the cartridge itself.

An alternative toner adding hardware item has been proposed in the past,a toner adder brush roller, also known as a toner supply brush roller.U.S. Pat. No. 4,083,326 discloses an “electrically conductive fur brush”roller loaded with brush materials made of natural and synthetic fibers,and also made of fibers extruded and containing conductive particlessuch as carbon. Thus, instead of attaching a conductive foam cylinderonto a shaft as done in making the toner adder roller, a toner adderbrush roller may be made by loading and adhering conductive filaments orfibers perpendicularly to the shaft. This can be done by two processes:wrapping a woven ‘velvet’ strip around the shaft or fixating thefilaments directly onto the shaft through a flocculation process.

The toner adder brush roller possesses a number of characteristics thatmake it appear to be a potential solution to the toner starvationproblem encountered by the toner adder roller. The softer nature of thefilaments noticeably reduces the torque in the toner adder brushroller/developer roller nip, compared to a system utilizing the toneradder roller. The greatly increased surface area also has the potentialto improve the capability of the toner adder brush roller to chargetriboelectrically compared to the toner adder roller, sincetriboelectric charge is a surface phenomenon.

However, the flocked and the woven toner adder brush roller each possessa unique set of characteristics that may lead either to severe printquality defects or to system failure. In the case of the flocked toneradder brush roller and depending on the toner, the toner that ends upbetween the densely populated toner adder brush roller filaments cannotget back out. Consequently, toner packing occurs with the result thatthe flocked toner adder brush roller is essentially transformed into asolid cylinder. In the case of the woven toner adder brush roller,wherein a woven fabric is cut into bands and wrapped around and adheredto the shaft in a spiral configuration, wrap pattern print defects occuras a function of the gap formed between the fabric edges. Thus, there isa need to find a toner adder brush configuration that combines thewanted characteristics of each existing version while eliminating theproperties that cause problems.

As a result, there is a need for an innovation that will overcome theabove-mentioned defects for providing a solution to the toner starvationproblem encountered by laser printer toner cartridge systems.

SUMMARY OF THE INVENTION

The present invention meets this need by providing an innovation thatsubstantially overcomes the above-mentioned drawbacks of toner packingand/or wrap pattern print defects in flocked and woven toner adder brushrollers by combining the flocked and woven configurations of toner adderbrush rollers to provide an enhanced toner adder brush roller whichwill, in turn, substantially overcome the toner starvation problem. Thetoner packing problem is believed to be based on inadequate filamentinterspacing within the flocked filament population on the shaft of thetoner adder brush roller over the surface of the shaft. Poor filamentinterspacing and lack of population control are a direct result of theshortcomings of the flocculation process itself. Although theflocculation process is self-terminating, it does not ensure an adequatenumber of filaments in the filament population. The innovation of thepresent invention contributes to a controlled installation of a filamentpopulation on the shaft for making the enhanced toner adder brushroller. In addition, with the process described herein, it is believedthat a controlled mix of two or more different filament sets to be fixedon the brush roller shaft surface can be achieved. The differencebetween the filament populations can be in the type of material, inphysical or electrical characteristics (denier variations and/or lengthvariations) or in combinations of these.

Accordingly, in an aspect of the present invention, a method forcontrolled installation of a brush filament population on a roller shaftfor making a toner adder brush roller comprises applying a template overat least a portion of the shaft surface, applying a layer of adhesiveover a surface of a roller shaft and template, removing the templatefrom the shaft surface and flocking a multiplicity of filaments on theshaft surface to provide a brush on the roller shaft having a filamentpopulation controlled by the application of the template. The methodalso includes removing the template from the shaft surface afterflocking the multiplicity of filaments such that a set of filaments lessthan the multiplicity of filaments is removed with the template. Themethod further allows for flocking additional filaments on the portionof the shaft surface after removing the template from the portion of theshaft surface.

In another aspect of the present invention, a toner adder brush rollerincludes a shaft made from or plated with a suitableelectrically-conductive metal adapted to support an electric field, alayer of adhesive coating the surface of said shaft, and a multiplicityof filaments flocked on and attached to the layer of adhesive on theshaft so as to provide a filament population controlled by a templateapplied over the shaft. The filaments are adapted to support a bipolararrangement of electrical charge. The electric field of the shaftinduces the bipolar arrangement of charge in the filaments causing theattached filaments to be electrically oriented relative to the electricfield of the shaft.

BRIEF DESCRIPTION OF THE DRAWINGS

Having thus described the invention in general terms, reference will nowbe made to the accompanying drawings, which are not necessarily drawn toscale, and wherein:

FIG. 1 is a simplified enlarged schematic representation of a prior artflocculation process for planting filaments on a conductive shaft formaking a prior art toner adder brush roller;

FIG. 2 a is a block diagram of a method for controlled installation of afilament population on a shaft for making an enhanced toner adder brushroller in accordance with the present invention;

FIG. 2 b is a block diagram of an alternate method for controlledinstallation of a filament population on a shaft for making an enhancedtoner adder brush roller in accordance with the present invention;

FIG. 3 is an exemplary embodiment of an enhanced toner adder brushroller of the present invention made by the method of FIG. 2 a;

FIG. 4 is a fragmentary schematic representation of an exemplaryembodiment of the toner adder brush roller after filament flocculationon to the adhesive layer but prior to removal of an exemplary templatethat had been applied over the surface of the shaft in accordance withthe method described in FIG. 2 a; and

FIG. 5 a is a fragmentary schematic representation of an exemplaryembodiment of the toner adder brush roller after a first flocculation offilaments on the adhesive layer where an exemplary template had beenapplied over the adhesive layer on the surface of the shaft of theenhanced toner adder brush roller in accordance with the methoddescribed in FIG. 2 b; and

FIG. 5 b is a fragmentary schematic representation of an exemplaryembodiment of the toner adder brush roller after the exemplary templatehad been removed and a second flocculation of different filaments hasbeen applied to the adhesive layer that had been covered by the templatein accordance with the method described in FIG. 2 b.

DETAILED DESCRIPTION

The present invention now will be described more fully hereinafter withreference to the accompanying drawings, in which some, but not allembodiments of the invention are shown. Indeed, the invention may beembodied in many different forms and should not be construed as limitedto the embodiments set forth herein; rather, these embodiments areprovided so that this disclosure will satisfy applicable legalrequirements. Like numerals refer to like elements throughout the views.

Basically, as shown in the simplified schematic representation of FIG.1, a prior art flocculation process, also known as “electrostaticplanting” or “flocking”, is carried out by applying an electric field toan electrically-conductive shaft 10. The conductive shaft 10 is madefrom or plated with a suitable electrically-conductive metal, such asnickel, cobalt, copper and the like. As described herein shaft 10 iscylindrical with a circular cross-section. With the process disclosedherein, it is expected that shafts having other cross-section shapessuch as square, triangular, rectangular could also be used. The surface10 a of the shaft 10 is pre-coated with a non-cured adhesive layer 12.Conductive filaments 14 to be planted or flocked onto the adhesive layer12 of the shaft 10 are pre-cut to a final length and surface treated toact as a non-conductive material. The electrically-conductive shaft 10and the filaments 14 are placed in a fluid medium 16 indicated by thedashed line box, such as a gas, air or the like, located within theelectric field applied to the shaft 10. The electric field induces abipolar charge in the filaments 14, causing them to turn the end withopposing charge relative to the charge of the shaft 10 and toward theshaft 10. The filaments 14 will move through the fluid medium 16 andland on the shaft 10 and plant into the adhesive layer 12 in aperpendicular (or radial) orientation relative to the shaft surface 10a. The adhesive layer 12 on the shaft surface 10 a fixes the filaments14 to the shaft 10 thus ensuring that the filaments 14 do not repel fromthe shaft 10. It will be realized that the flocked filaments will beradially aligned on the curved surface of the shaft.

While the flocculation process is a self-terminating process, it willnot ensure a homogeneous population of filaments 14 on the shaft 10until the flocking is complete, that is, when each vacant site on theshaft 10 has been populated and filament packing has reached itsmaximum. The flocculation process has another limitation: flocculationis easier to carry out the shorter the cut filaments 14 are. Longerfilaments have a larger probability of rubbing against each other whilemoving in the fluid medium 16 towards the shaft 10. This will adverselyaffect the alignment of the filaments 14 on the shaft 10. So for a givenpopulation of filaments it is important to cut the filaments 14 to thedesired length; the more homogeneous the filament population isregarding length, the more homogeneous will be the diameter of thefinished toner adder brush roller 18 in those areas where thosefilaments are used.

FIGS. 2 a, 3, and 4 respectively illustrate a block diagram of a methodfor controlled installation of a filament population on the shaft 10 andan enhanced toner adder brush roller 20 made by the method, both inaccordance with the present invention. Since the flocculation processwould terminate when filaments 14 have been completely packed (or fullypopulated) over the entire shaft surface 10 a, it appears possible tocontrol filament population per unit of toner adder brush roller shaftsurface area (# filaments/shaft unit area) by selecting and controllingthe areas on the surface 10 a of the shaft 10 where the adhesive layer12 will be applied. Therefore, an embodiment of the method for makingthe enhanced toner adder brush roller 20 includes the steps of: as perblock 100 a, applying the template 22 over the surface 10 a of the shaft10 to cover at least a first portion 24 of the surface 10 a of the shaft10 and leave a second portion 26 of the shaft surface 10 a exposed; asper block 102 a, applying the adhesive layer 12 over the template 22 andexposed second portion 26 of the shaft surface 10 a, as per block 104 a,removing the template 22 from the shaft 10, and as per block 106 a,flocking a multiplicity of filaments 14 in the adhesive coated exposedsecond portion 26 of the shaft surface 10 a by utilizing theflocculation process depicted in FIG. 1. As can be seen in FIG. 3, thetoner adder brush roller 10 has first portions 24 that do not containany filaments and second portions 26 that are populated by amultiplicity of filaments 14.

As illustrated in FIGS. 2 b, 5 a and 5 b, an alternate embodiment of themethod for making the enhanced toner adder brush roller 20 includes thesteps of: as per block 10 b, applying the adhesive layer 12 to the shaftsurface 10 a, as per block 102 b, applying the template 22 over theadhesive layer 12 covering at least a first portion 28 of the adhesivelayer 12 while leaving a second portion 30 of the adhesive layerexposed, as per block 104 b, flocking a multiplicity of filaments on theexposed second portions of the adhesive layer 12, as per block 106 b,removing the template 22 from the shaft surface 10 a to expose the firstportion 28 of the adhesive layer 12, and, as per block 108 b, flockingan additional multiplicity of filaments 14 on the exposed first portion28 of the adhesive layer 12.

As shown in FIG. 5 b filaments 15 have been flocked onto portions 28 ofthe adhesive layer. Filaments 15 can be the same as type as filaments 14but have a different length or denier than filaments 14 or can be of adifferent type, and/or length and/or denier. The shaft will likely haveto be populated to the maximum, meaning no open sites remaining as eachportion of the adhesive layer is exposed to the filaments of a giventype. However, the filaments 14 may be flocked onto the entire shaft 10but will only adhere to the areas of the shaft 10 where adhesive layer12 is applied, thus creating an enhanced toner adder brush roller 20with a lower filament population count. This method may be extended toinclude several additional sets of filaments 14 or 15.

The filaments 14, 15 may be made by a well-known spinning process as along continuous filament thread and wrapped around a large wheel (like aroll of thread) to facilitate handling thereof. To use the filament tomake a flocked brush roller, the long continuous filament is cut intovery precise and very short sections. The filament is unwrapped from thewheel into a large skein, which in turn is twisted hard, clamped down,and cut into small and very precise sections. In other words, all of thesmall filaments were initially from a long strand. Finally, thefilaments are pre-treated to ensure that they do not act as if they areconductive. If they are conductive, the filament will not act as adipole and will not align properly to the electrical field.

In the above-described steps of the method, there are severalalternative ways to control the placement of the filament population onthe surface 10 a of the toner adder brush roller shaft 10. Desiredfilament-free 24 areas may be created across the shaft surface 10 a byselectively locating the adhesive layer 12 on the roller shaft 10 usingone or more of these techniques: (a) by printing the adhesive layer 12in a controlled pattern over the shaft 10; (b) by spraying the adhesivelayer 12 in a controlled pattern over the shaft 10; or (c) by applyingthe template 22 over the shaft 10 either before or after the printing orspraying. The template 22 will enable the adhesive layer 12 to beapplied in a controlled pattern over the shaft 10. The template 22 maybe removed either after the application of the adhesive layer 12 iscomplete or after the flocculation process has been completed. Also, thetemplate 22 may not be removed. This would not permit application of asecond set of filaments as the template 22 will be part of the finishedenhanced toner adder brush roller 20. In some instances, the templateand shaft are coated in a second layer of adhesive. In addition, thetechnique as described in (c) above may enable construction of anenhanced toner adder brush roller 20 with a homogeneous flocked filamentblend configuration. A possible benefit where the template 22 is coatedwith the adhesive layer 12 is that the filaments 14 that do not hit anexposed section of the shaft 10 will still be attached perpendicularlyto the shaft 10, but on the template 22 (see FIG. 4). This mechanism mayminimize the amount of filaments 14 that will repel against theshaft/template surface and thus travel (be thrown) back into theelectrical field. Repelled filaments may disturb the alignment offilaments traveling through the electrical field towards the shaft 10,thereby increasing the risks of a poorly aligned filament population onthe finished toner adder brush roller 20.

If the template 22 is not removed from the shaft 10, then variation inheight of the filaments 14 can be achieved by using of the thickness ofthe template 10 itself, allowing for filaments of one given length tohave at least two different heights when flocked and adhering to thetoner adder roller brush 20 as illustrated in FIG. 4. Further if thetemplate 10 is made in a manner such that its thickness is variable overits area then the height of the filaments adhering there will vary inthe same manner. It is contemplated that the template may also containregions of constant thickness and regions of variable thickness. Thevariable thickness can be achieved in a step-wise fashion such that thelower surfaces are level but parallel to the outer surface of thetemplate or by using concavities or convexities or concavoconvexities orcombinations thereof. The outer surface of the template is the surfaceaway from the shaft surface while the inner surface of the template isthe surface that faces or is adjacent to the shaft surface. It would beexpected that where concavities, convexities or concavoconvexities areused the filaments flocked on to those areas will not be radiallyaligned to the filaments flocked onto the shaft surface or the regionsof constant thickness of the template.

The differences between the filaments 14 that may be flocked onto thesame shaft 10 include, but are not limited to, material includingchemical and electrical properties thereof, filament length and denier.The above-described method is applicable to filaments 14, 15 having awide range of synthetic chemical compositions, such as acrylic, PU,nylon and the like, and of filament properties and configurations, suchas denier range, shape, resistance level and the like. An exemplaryembodiment of a filament population is in the range of about 15 KF to150 KF (1 KF=1000 filaments/in.²) for a six denier filament (1 denier=1g/9000 m). The filament surface may also be chemically treated to helpachieve the desired properties.

FIGS. 4 and 5 a illustrate exemplary embodiments of fragmentary sectionsof the template 22 respectively under and over the adhesive layer 12.The template 22 should ideally be reusable (thus should be sturdy butflexible) and may, for example, be made from metal, polymer, or paper.However, the template 22 usually is not reusable when it has beenapplied under the adhesive layer 12. The template 22 should not cut offthe electrical field generated around the shaft 10 or the flocculationprocess may get disturbed diminishing the functionality of the finishedtoner adder brush roller 20. The pattern of the template 22 may bedesigned in a number of different ways, for example, contain slots(which includes holes and the like), aligned in a pattern, such as acubic or diamond pattern as shown in FIG. 3. The pattern may be etchedon or punched out of a continuous sheet of template material. It mayalso be possible to mold a template pre-cursor into a pattern. Lastly,the template 22 (and therefore also the pattern) may be oriented in anyangle with respect to the shaft 10.

Using the method of the present invention other variations are possible.Different filaments 14, 15 may be placed at different locations alongthe length of the shaft or core, such as one filament type near each endand another type in the center, although a homogeneous population overthe entire shaft surface 10 a is preferred. Also, the filaments 14 maybe alternated like stripes along the length of the shaft 10. Also, thestripes may spiral about the shaft 10. Further, combinations of thesemay be used, a pattern of stripes in one region and a different patternin another region. Also, the filament length may vary in different areasor a combination of filament lengths may be used in a given area. Thefilaments 14 preferably are perpendicular to the shaft surface 10 aalthough they may be angled or in a more random, tangled or mattedpattern, if desired.

The adhesive may be either conductive or non-conductive. It also needsto be sticky (higher viscosity) so that it fixes the filament to theshaft 10 as soon as the filament hits the adhesive surface, in view thatthe shaft 10 will repel the filament as soon as it hits the surface. Atthe same time, the adhesive needs to be kept at a viscosity that ensuresa thin and homogeneous thickness over the shaft 10. The filament doesnot have to penetrate through the adhesive layer 12 all the way to theshaft surface 10 a in order to ensure a conductive path between theshaft and filament ends. The most cost effective adhesive to use is anon-conductive hot-melt adhesive (however a conductive hot-melt adhesivemay also be used). A hot-melt adhesive can be applied to the shaftsurface 10 a, let cool down and harden, get heated up again (activated)and fixed to the other surface (the filament), to finally be cooled downagain (cured). As long as the shaft temperature in the cartridge when itis operating in the printer does not exceed the adhesive re-activationtemperature, the hot-melt adhesive works effectively.

In summary, the present invention is directed to a controlled method ofinstalling a brush filament population on a shaft for making an enhancedtoner adder brush roller having an improved filament population densityand placement controlled by the application of a template. The problemsolved is that print quality is improved due to reduced tonerstarvation, improved toner charge consistency, and reduced heatgeneration in view that torque is reduced. The use of the toner adderbrush roller potentially will improve print quality performance andreduce system torque thus further enabling printers to go to higherspeeds.

The foregoing description of several embodiments of the invention hasbeen presented for purposes of illustration. It is not intended to beexhaustive or to limit the invention to the precise forms disclosed, andobviously many modifications and variations are possible in light of theabove teaching. It is intended that the scope of the invention bedefined by the claims appended hereto.

1. A toner adder brush roller, comprising: a shaft made from or platedwith a suitable electrically-conductive metal adapted to support anelectric field; a layer of adhesive coating the surface of said shaft;and a multiplicity of brush filaments flocked on and attached to saidlayer of adhesive on said shaft so as to provide at least a firstfilament population and a second filament population, the filaments ofthe first filament population differing from the filaments of the secondfilament population in at least one of height and type, each of saidfilaments supporting a bipolar arrangement of electrical charge, saidelectric field of said shaft inducing the bipolar arrangement of chargein said each filament causing said attached filaments to be electricallyoriented relative to said electric field of said shaft.
 2. The roller ofclaim 1 wherein said filaments of the first and second filamentpopulations are pre-cut to a final length before attachment to saidlayer of adhesive.
 3. The roller of claim 1 wherein said filaments ofthe first and second filament populations are surface treated, to act asa non-conductive material, before attachment to said layer of adhesive,to support said bipolar arrangement of electrical charge.
 4. The rollerof claim 1 wherein said layer of adhesive is a hot-melt adhesive.
 5. Theroller of claim 1 wherein said filaments of the first and secondfilament populations are of a synthetic chemical composition.
 6. A toneradder brush roller, comprising: a shaft comprisingelectrically-conductive metal adapted to support an electric field; alayer of adhesive coating the surface of said shaft; and a multiplicityof brush filaments flocked on and attached to said layer of adhesive onsaid shaft so as to provide at least a first filament population and asecond filament population, the second filament population differingfrom the first filament population by at least one of material, length,or denier, each of said filaments supporting a bipolar arrangement ofelectrical charge, said electric field of said shaft inducing thebipolar arrangement of charge in said each filament causing saidattached filaments to be electrically oriented relative to said electricfield of said shaft.
 7. The toner adder brush roller of claim 6 furthercomprising a template applied over said adhesive layer covering at leastone portion of the adhesive layer of the shaft.
 8. The toner adder brushroller of claim 6 further comprising a template applied to the surfaceof the shaft under said adhesive layer, wherein said template covers afirst portion of the shaft surface and includes one or more slotstherethrough positioned over a second portion of the shaft surface, thetemplate forming part of the toner adder brush roller under the brushfilaments.
 9. The toner adder brush roller of claim 8 wherein saidtemplate has a variable thickness over its surface.
 10. The toner adderbrush roller of claim 8 wherein the template has a constant thicknessover its surface.
 11. The toner adder brush roller of claim 8 whereinthe applied template has at least one region of constant thickness andat least one second region of variable thickness over its surface.